Coating formulation for preparing a hydrophilic coating

ABSTRACT

The invention is directed to a coating formulation for preparing a hydrophilic coating a hydrophilic polymer, a Norrish Type II photoinitiator, comprising a substituted benzohenone, xanthone, tioxanthone or anthraquinone, and more than 70 wt % of a carrier liquid; to a method of forming a hydrophilic coating on a substrate, the method comprising: applying a coating formulation to at least one surface of an article and allowing the coating formulation to cure for a time period less than 360 seconds; and to an article comprising at least one hydrophilic coating.

The invention is directed to a coating formulation for preparing ahydrophilic coating, a method to apply the coating formulation to asurface, a lubricious coating obtainable by applying a wetting fluid toa hydrophilic coating and an article, in particular a medical device,comprising a hydrophilic or lubricious coating.

Many medical devices, such as guide wires, urinary and cardiovascularcatheters, syringes, and membranes need to have a lubricant applied tothe outer and/or inner surface to facilitate insertion of these medicaldevices into and removal from the body. The lubricants also facilitatedrainage of fluids from the body. Lubricious properties are alsorequired to minimize soft tissue damage upon insertion or removal. Forlubrication purposes medical devices often contain a hydrophilic surfacecoating or layer which becomes lubricious and attains low-frictionproperties upon wetting, i.e. by applying a wetting fluid for a certaintime period prior to insertion of the device into the body of a patient.

A coating or layer which becomes lubricious after wetting is hereinafterreferred to as a hydrophilic coating. A coating obtained after wettingis hereinafter referred to as a lubricious coating.

In applications where a coating comes into contact with liquids, thereis a desire to minimize the amount of migrateables. The term“migrateables” as used herein is recognized in the art to indicatemolecules that may leak out of a particular matrix under particularcircumstances. The term is synonymous with “extractables” or“extractable components” which terms are also frequently used in theart.

In coatings used in membranes and in films that are in contact with foodthe amount of migrateables should be as low as possible. The desire tominimize the amount of migrateables becomes extremely important when thecoatings are used in medical devices that are used medical applications.Medical devices that come into close contact with the body or bodyfluids are, for instance, contact lenses, guide wires and catheters. Theloss of one or more components from a coating may result in change incomposition and functional properties of the coating as well as incontaminating the immediate host environment. Moreover, the migrateablecomponent may be harmful when released into the environment of thecoating, such as food, human body or body fluids.

The most common way to reduce the amount of migrateables from a coatingis by crosslinking a coating formulation by curing. The term “to cure”includes any way of treating the formulation such that it forms a firmor solid coating whereby the ability of the dried coating components todissolve again in a solvent is completely eliminated or stronglyreduced. In particular, the term includes a treatment whereby thehydrophilic polymer crosslinks by a process called grafting whereinpolymer chains are chemically connected under the influence of areactive entity.

This can, for instance, be performed by adding photoinitiators to acoating formulation, which subsequently are activated by electromagneticradiation after a coating formulation is applied on a substrate. Acoating prepared in such way adheres to the surface well enough toresist mechanical or other abrasive forces applied to the surface andthe amount of migrateables released from the coating is minimized.

Coating formulations comprising photoinitiators are, for instance,described in WO2006/056482 and WO2009/112548. In these patentpublications the use of different types of photoinitiators is describedfor curing hydrophilic coating formulations.

It has now surprisingly been discovered that by using a special type ofphotoinitiators the curing time of a coating formulation can besignificantly improved.

The invention is characterized by a coating formulation for preparing ahydrophilic coating comprising a hydrophilic polymer, a Norrish Type IIphotoinitiator, comprising a substituted benzohenone, xanthone,tioxanthone or anthraquinone, and more than 70 wt % of a carrier liquid.

The advantage of using the coating formulation according to theinvention is that the cure speed of the coating formulation improvessignificantly. The hydrophilic coating can thus be applied on asubstrate in a shorter amount of time. This results in a faster coatingprocess which is economically attractive.

The coating formulation according to the invention comprises a Norrishtype II photoinitiator. A type II photoinitiator induces crosslinking incase it is activated with electromagnetic radiation by hydrogenabstraction from a suitable synergist, which may be a low molecularweight compound or a polymer.

The substituents on the Norrish type II photoinitiator can be present onthe 2, 3 and/or 4 position of the phenyl rings in the Norrish Type IIphotoinitiator, preferably on the 3 and/or 4 position of the phenylrings. Examples of substituents are substituents comprising hydroxy,anhydride, acid, ester, ether, amine, amide and amino functional groups.Examples of Type II photoinitiators are 2-benzoyl benzoic acid,3-benzoyl benzoic acid, 4-benzoyl benzoic acid, 3,3′,4,4′-benzophenonetetracarboxilic acid, 4-benzoyl-N,N,N,-trimethylbenzene-methaminiumchloride, 2-hydroxy-3-(4-benzoylphenoxy)-N,N,N-trimethyl-1-propanaminiumchloride,2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthon-2-yloxy)-N,N,N-trimethyl-1-propanaminiumchloride, thioxanthone-3-carboxylic acid, thioxanthone-4-carboxylicacid, anthraquinone 2-sulfonic acid, 9,10-anthraquinone-2,6-disulphonicacid, anthraquinone-2-sulfonic acid, anthraquinone-2-carboxylic acid andsalts of these derivatives such as the sodium-, potassium-, calcium-,magnesium, iron-, copper and zinc salts.

Norrish Type II photoinitiators that bear more than one substituent canalso be used.

Also mixtures of Norrish Type II photoinitiators can be used.

The cure speed of the coating formulation can be further improved if thecoating formulation also comprises a Norrish type I photo initiator.

In such a coating formulation both the Norrish Type II photoinitiatorsand Norrish Type I photoinitiators are free-radical photoinitiators, butare distinguished by the process by which the initiating radicals areformed.

Compounds that undergo unimolecular bond cleavage of the chromophoreupon irradiation to generate radicals that initiate polymerization aretermed Norrish Type I or homolytic photoinitiators. The Norrish Type IIphotoinitiators generate radicals indirectly by hydrogen abstractionfrom a suitable synergist, which may be a low molecular weight compoundor a polymer.

Compounds that undergo unimolecular bond cleavage upon irradiation aretermed Norrish Type I or homolytic photoinitiators, as shown by formula(1):

Depending on the nature of the functional group and its location in themolecule relative to the carbonyl group, the fragmentation can takeplace at a bond adjacent to the carbonyl group (α-cleavage), at a bondin the β-position (β-cleavage) or, in the case of particularly weakbonds (like C—S bonds or O—O bonds), elsewhere at a remote position. Themost important fragmentation in photoinitiator molecules is theα-cleavage of the carbon-carbon bond between the carbonyl group and thealkyl residue in alkyl aryl ketones, which is known as the Norrish TypeI reaction.

Examples of suitable Norrish Type I or free-radical photoinitiators arebenzoin derivatives, methylolbenzoin and 4-benzoyl-1,3-dioxolanederivatives, benzilketals, α,α-dialkoxyacetophenones, α-hydroxyalkylphenones, α-aminoalkylphenones, acylphosphine oxides,bisacylphosphine oxides, acylphosphine sulphides, halogenatedacetophenone derivatives, and the like. Commercial examples of suitableType I photoinitiators are Irgacure 2959(2-hydroxy-4′-(2-hydroxyethoxy)-2-methyl propiophenone), Irgacure 651(benzildimethyl ketal or 2,2-dimethoxy-1,2-diphenylethanone,Ciba-Geigy), Irgacure 184 (1-hydroxy-cyclohexyl-phenyl ketone as theactive component, Ciba-Geigy), Darocur 1173(2-hydroxy-2-methyl-1-phenylpropan-1-one as the active component,Ciba-Geigy), Irgacure 907(2-methyl-1-[4-(methylthio)phenyl]-2-morpholino propan-1-one,Ciba-Geigy), Irgacure 369(2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one as theactive component, Ciba-Geigy), Esacure KIP 150(poly{2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propan-1-one},Fratelli Lamberti), Esacure KIP 100 F (blend ofpoly{2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propan-1-one} and2-hydroxy-2-methyl-1-phenyl-propan-1-one, Fratelli Lamberti), EsacureKTO 46 (blend ofpoly{2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propan-1-one},2,4,6-trimethylbenzoyldiphenyl-phosphine oxide and methylbenzophenonederivatives, Fratelli Lamberti), acylphosphine oxides such as LucirinTPO (2,4,6-trimethylbenzoyl diphenyl phosphine oxide, BASF), Irgacure819 (bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine-oxide, Ciba-Geigy),Irgacure 1700 (25:75% blend ofbis(2,6-dimethoxybenzoyl)2,4,4-trimethyl-pentyl phosphine oxide and2-hydroxy-2-methyl-1-phenyl-propan-1-one, Ciba-Geigy), and the like.Also mixtures of type I photoinitiators can be used.

The amount of the Norrish Type II photoinitiator in the coatingformulation comprising the carrier liquid is preferably higher than 0.01wt %, more preferably higher than 0.02 wt %, of that coatingformulation. The amount of the Norrish Type II photoinitiator in thecoating formulation comprising the carrier liquid is preferably lowerthan 0.5 wt %, more preferably lower than 0.2 wt %.

The amount of the Norrish Type II photoinitiator and, if present, theNorrish type I photoinitiator in the hydrophilic coating formulation isbetween 0.1 and 10 wt %, preferably between 0.5 and 5 wt %, mostpreferably between 0.5 and 3 wt % based on the total dry weight of thecoating. The dry weight is defined as the weight comprising allcomponents of the coating formulation excluding the carrier liquid.

Typically the weight ratio of Norrish Type I photoinitiator to theNorrish Type II photoinitiator is between 10:1 and 1:10; preferablybetween 7:1 and 1:7 and more preferably between 5:1 and 1:5; mostpreferably between 2:1 and 1:2.

The coating formulation further comprises a hydrophilic polymer. Hereina hydrophilic polymer is understood to be a high molecular weightlinear, branched or cross-linked polymer composed of macromolecules.Hydrophilic polymers have an affinity for water or other polar liquidsand as such do attract and/or absorb water when used in a coating on asurface.

The hydrophilic polymer is capable of providing hydrophilicity to acoating and may be synthetic or bio-derived. The hydrophilic polymer canbe a blend of polymers or contain copolymers. The hydrophilic polymersinclude but are not limited to poly(lactams), for examplepolyvinylpyrollidone (PVP), polyurethanes, homo- and copolymers ofacrylic and methacrylic acid, polyvinyl alcohol, polyvinylethers, maleicanhydride based copolymers, polyesters, vinylamines, polyethyleneimines,polyethyleneoxides, poly(carboxylic acids), polyamides, polyanhydrides,polyphosphazenes, cellulosics, for example methyl cellulose,carboxymethyl cellulose, hydroxymethyl cellulose, andhydroxypropylcellulose, heparin, dextran, polypeptides, for examplecollagens, fibrins, and elastin, polysacharrides, for example chitosan,hyaluronic acid, alginates, gelatin, and chitin, polyesters, for examplepolylactides, polyglycolides, and polycaprolactones, polypeptides, forexample collagen, albumin, oligo peptides, polypeptides, short chainpeptides, proteins, and oligonucleotides.

Generally the hydrophilic polymer has a molecular weight in the range ofabout 8,000 to about 5,000,000 g/mol, preferably in the range of about20,000 to about 3,000,000 g/mol and more preferably in the range ofabout 200,000 to about 2,000,000 g/mol.

The coating formulation comprising the carrier liquid generallycomprises 2-10 wt %, preferably 3-8 wt %, of a hydrophilic polymer.

In a dry hydrophilic coating that is present on a substrate thehydrophilic polymer may be present in more than 1 wt %, for example morethan 5 wt %, or more than 50 wt %, based on the total dry weight of thecoating. The hydrophilic polymer can be present up to 99 wt %, or up to95 wt %, based on the total dry weight of the coating.

The formulation further comprises a carrier liquid in a sufficientamount to disperse or dissolve the other components of the formulation.The carrier liquid concentration is at least 70 wt. %, preferably atleast 75 wt. %, more preferably at least 80 wt. %, even more preferablyat least 85 wt. % of the total weight of the coating formulation. Inview of handling properties (low viscosity) and/or in order tofacilitate the application of the composition such that a coating withthe desired thickness is obtained, the amount of carrier liquid in thecomposition is preferably relatively high. For that reason the totalsolids content is preferably 20 wt. % or less.

The carrier liquid comprises water. The water may be the single solventor a mixture with another solvent. The water content in the carrierliquid is normally chosen between 20 and 100 wt % based on the totalamount of carrier liquid. Preferably the water content in the carrierliquid is between 20 and 80 wt %, more preferably between 40 and 60 wt%.

The carrier liquid(s) are chosen such that the polymers can be dissolvedor at least dispersed therein. In particular for dissolving ordispersing the hydrophilic polymer well, it is preferred that thecarrier liquid(s) are polar liquids. In particular, a liquid isconsidered polar if it is soluble in water. Apart from water, thecarrier liquid preferably comprises an organic liquid soluble in water,more preferably an alcohol, most preferably a C1-C4 alcohol, inparticular methanol and/or ethanol and/or isopropanol.

The hydrophilic coating formulation according to the invention may alsocomprise a polyelectrolyte. Herein a polyelectrolyte is understood to bea high molecular weight linear, branched or cross-linked polymercomposed of macromolecules comprising constitutional units, in whichbetween 5 and 100% of the constitutional units contain ionized groupswhen the polyelectrolyte is in the lubricious coating. Herein aconstitutional unit is understood to be a repeating unit, for example amonomer. A polyelectrolyte herein may refer to one type ofpolyelectrolyte composed of one type of macromolecules, but it may alsorefer to two or more different types of polyelectrolytes composed ofdifferent types of macromolecules.

The use of a polyelectrolyte may be considered to improve the lubricityand the dry-out time of the hydrophilic coating. Herein dry-out time isdefined as the duration that a hydrophilic coating remains lubricious inthe open air after the device comprising the hydrophilic coating hasbeen taken out of the wetting fluid wherein it has been stored and/orwetted. Hydrophilic coatings with an improved dry-out time, i.e. whereinthe duration that the hydrophilic coating remains lubricious is longer,will have a lower tendency of losing water and drying out prior toinsertion into the body, or in the body when it comes in contact withe.g. a mucous membrane or vein. When the dry-out time of a hydrophiliccoating is low it may result in complications when the device comprisingthe lubricious coating is inserted into the body or removed from thebody. The dry-out time can be determined in a Harland Friction Test(HFT) by measuring the friction in gram as a function of the time thatthe catheter is exposed to air.

Considerations when selecting a suitable polyelectrolyte are itssolubility and viscosity in aqueous media, its molecular weight, itscharge density, its affinity with the supporting network of the coatingand its biocompatibility. Herein biocompatibility means biologicalcompatibility by not producing a toxic, injurous or immunologicalresponse in living mammalian tissue.

To obtain a hydrophilic coating with a low amount of migrateables, thepolyelectrolyte is preferably a polymer having a weight averagemolecular weight of at least about 1000 g/mol, as can be determined bylight scattering, optionally in combination with size exclusionchromatography. A relatively high molecular weight polyelectrolyte ispreferred for increasing the dry-out time and/or reduced migration outof the coating. The weight average molecular weight of thepolyelectrolyte is preferably at least 20,000 g/mol, more preferably atleast 100,000 g/mol, even more preferably at least about 150,000 g/mol,in particular about 200,000 g/mol or more. To be able to apply thecoating easy it is preferred that the average weight is 1000,000 g/molor less, in particular 500,000 g/mol or less, more in particular 300,000g/mol or less.

Examples of ionized groups that may be present in the polyelectrolyteare ammonium groups, phosphonium groups, sulfonium groups, carboxylategroups, sulfate groups, sulfinic groups, sulfonic groups, phosphategroups, and phosphonic groups. Such groups are very effective in bindingwater. In one embodiment of the invention a polyelectrolyte is used thatalso comprises metal ions. Metal ions that may be present in thepolyelectrolyte are for example alkali metal ions, such as Na⁺, Li⁺, orK⁺, or alkaline earth metal ions, such as Ca²⁺ and Mg²⁺. In particularwhen the polyelectrolyte comprises quaternary amine salts, for examplequaternary ammonium groups, anions may be present. Such anions can forexample be halogenides, such as Cl⁻, Br⁻, I⁻ and F⁻, and also sulphates,nitrates, carbonates and phosphates.

Suitable polyelectrolytes are for example salts of homo- and co-polymersof acrylic acid, salts of homo- and co-polymers of methacrylic acid,salts of homo- and co-polymers of maleic acid, salts of homo- andco-polymers of fumaric acid, salts of homo- and co-polymers of monomerscomprising sulfonic acid groups, homo- and co-polymers of monomerscomprising quarternary ammonium salts and mixtures and/or derivativesthereof. Examples of suitable polyelectrolytes arepoly(acrylamide-co-acrylic acid)salts, for examplepoly(acrylamide-co-acrylic acid) sodium salt,poly(acrylamide-co-methacrylic acid) salts, for examplepoly(acrylamide-co-methacrylic acid) sodium salt,poly(methacrylamide-co-acrylic acid) salts, for examplepoly(methacrylamide-co-acrylic acid) sodium salt,poly(methacrylamide-co-methacrylic acid) salts, for examplepoly(methacrylamide-co-methacrylic acid) sodium salt poly(acrylic acid)salts, for example poly(acrylic acid) sodium salt, poly(methacrylicacid) salts, for example poly(methacrylic acid) sodium salt,poly(acrylic acid-co-maleic acid) salts, for example poly(acrylicacid-co-maleic acid) sodium salt, poly(methacrylic acid-co-maleic acid)salts, for example poly(methacrylic acid-co-maleic acid) sodium salt,poly(acrylamide-co-maleic acid) salts, for examplepoly(acrylamide-co-maleic acid) sodium salt,poly(methacrylamide-co-maleic acid) salts, for examplepoly(methacrylamide-co-maleic acid) sodium salt,poly(acrylamido-2-methyl-1-propanesulfonic acid) salts, poly(4-styrenesulfonic acid) salts, poly(acrylamide-co-dialkyl ammonium chloride),quaternizedpoly[bis-(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl]urea],polyallylammonium phosphate, poly(diallyldimethylammonium chloride),poly(sodium trimethyleneoxyethylene sulfonate),poly(dimethyldodecyl(2-acrylamidoethyl)ammonium bromide), poly(2-Nmethylpyridiniumethylene iodine), polyvinylsulfonic acids, and salts ofpoly(vinyl)pyridines, polyethyleneimines, and polylysines.

Particularly suitable polyelectrolytes for use in the current inventionare copolymeric polyelectrolytes, which may be random or blockcopolymers, wherein said copolymeric polyelectrolyte is a copolymercomprising at least two different types of constitutional units, whereinat least one type of constitutional units comprises ionizable or ionizedgroups and at least one type of constitutional units is absent ofionizable or ionized groups. Herein “ionizable” is understood to beionizable in neutral aqueous solutions, i.e. solutions having a pHbetween 6 and 8. An example of such a copolymeric polyelectrolyte is apoly(acrylamide-co-acrylic acid) salt.

In one embodiment of the invention the hydrophilic coating compositioncomprises between 0 and 90 wt %, preferably 10-20 wt % ofpolyelectrolyte based on the total dry weight of the coating.

In the hydrophilic coating formulation the weight ratio of the totalweight of hydrophilic polymer to polyelectrolyte may, for example, varybetween 1:99 and 99:1, such as between 5:95 and 95:5 or 50:50 and 95:5.

Herein a hydrophilic coating formulation refers to a liquid hydrophiliccoating formulation, e.g. a solution or a dispersion comprising a liquidmedium. Herein any liquid medium that allows application of thehydrophilic coating formulation on a surface would suffice. Examples ofliquid media are alcohols, like methanol, ethanol, propanol, butanol orrespective isomers and aqueous mixtures thereof, acetone, methylethylketone, tetrahydrofuran, dichloromethane, toluene, and aqueous mixturesor emulsions thereof or water.

The invention is also directed to a method of forming a hydrophiliccoating on a substrate, the method comprising

-   -   applying a coating formulation to at least one surface of the        article and    -   allowing the coating formulation to cure for a time period less        than 360 seconds.

Preferably, the coating formulation is cured for a time period less than240 seconds, more preferably for a time period less than 200 seconds.The hydrophilic coating formulation can be applied to the substrate byfor example dip-coating. Other methods of application include spray,wash, vapor deposition, brush, roller and other methods known in theart.

The thickness of the hydrophilic coating according to the invention maybe controlled by altering the soaking time, drawing speed, or viscosityof the hydrophilic coating formulation and the number of coating steps.Typically the thickness of a dry hydrophilic coating on a substrateranges from 0.1-300 μm, preferably 0.5-100 μm, more preferably 1-30 μm,most preferably 1-15 μm.

The invention further relates to a method of forming on a substrate ahydrophilic coating which has a low coefficient of friction when wettedwith a water-based liquid.

To apply the hydrophilic coating on the substrate, a primer coating maybe used in order to provide a binding between the hydrophilic coatingand the substrate. The primer coating is often referred to as theprimary coating, base coat or tie coat. Said primer coating is a coatingthat facilitates adhesion of the hydrophilic coating to a givensubstrate. The binding between the primer coating and the hydrophiliccoating may occur due to covalent or ionic links, hydrogen bonding,physisorption or polymer entanglements. These primer coatings may besolvent based, water based (latexes or emulsions) or solvent free andmay comprise linear, branched and/or cross-linked components. Typicalprimer coatings that could be used comprise for example polyethersulfones, polyurethanes, polyesters, including polyacrylates, asdescribed in for example U.S. Pat. No. 6,287,285, polyamides,polyethers, polyolefins and copolymers of the mentioned polymers.

In particular, the primer coating comprises a supporting polymernetwork, the supporting network optionally comprising a functionalhydrophilic polymer entangled in the supporting polymer network asdescribed in WO2006/056482 A1.

A primer coating as described above is in particular useful forimproving adherence of a coating comprising a hydrophilic polymer suchas a polylactam, in particular PVP and/or another of the aboveidentified hydrophilic polymers, in particular on polyvinylchloride(PVC), silicone, polyamide, polyester, polyolefin, such as polyethylene,polypropylene and ethylene-propylene rubber (e.g. EPDM), or a surfacehaving about the same or a lower hydrophilicity.

In general there is no restriction as to the thickness of the primercoating, but typically the thickness is less than 5 μm, preferably lessthan 2 μm or, more preferably less than 1 μm.

In an embodiment, the surface of the article is subjected to oxidative,photo-oxidative and/or polarizing surface treatment, for example plasmaand/or corona treatment in order to improve the adherence of the coatingwhich is to be provided. Suitable conditions are known in the art.

Curing herein is understood to refer to physical or chemical hardeningor solidifying by any method, for example heating, cooling, drying,crystallization or curing as a result of a chemical reaction, such asradiation-curing or heat-curing. In the cured state all or part of thecomponents in the hydrophilic coating formulation may be cross-linkedforming covalent linkages between all or part of the components, forexample by using UV or electron beam radiation. However, in the curedstate all or part of the components may also be ionically bonded, bondedby dipole-dipole type interactions, or bonded via Van der Waals forcesor hydrogen bonds.

The term “to cure” includes any way of treating the formulation suchthat it forms a firm or solid coating. In particular, the term includesa treatment whereby the hydrophilic polymer further polymerizes, isprovided with grafts such that it forms a graft polymer and/or iscross-linked, such that it forms a cross-linked polymer.

Preferably, curing is performed by exposing the coating formulation toelectromagnetic radiation, more preferably to UV radiation.

Intensity and wavelength of the electromagnetic radiation can routinelybe chosen based on the photoinitiator of choice. In particular, asuitable wavelength in the UV, visible or IR part of the spectrum may beused.

The invention also relates to a hydrophilic coating obtainable byapplying the hydrophilic coating formulation according to the inventionto a substrate and curing it. The invention further relates to alubricious coating obtainable by applying a wetting fluid to saidhydrophilic coating. Further the invention relates to an article, inparticular a medical device or a medical device component comprising atleast one hydrophilic coating according to the invention.

The hydrophilic coating comprises a hydrophilic polymer. Saidhydrophilic coating is formed by curing a hydrophilic coatingformulation comprising the hydrophilic polymer, the Norrish Type IIphotoinitiator and, optionally, the Norrish Type I photoinitiator. If apolyelectrolyte is present this may also be covalently linked and/orphysically bound to one or more of the other components and/or entrappedto form a polymer network after curing.

The fact that the hydrophilic polymer and/or polyelectrolyte arecovalently and/or physically bound in the hydrophilic coating as part ofa polymer network has the advantage that they will not leak out into theenvironment of the hydrophilic coating, for example when it is coated ona medical device. This is particularly useful when the medical device isinside the human or animal body.

The hydrophilic coating can also comprise other additives, such as,supporting polymers, antimicrobial additives, pigments, coloring agents,surfactants and plasticizers.

The hydrophilic coating according to the invention can be coated on anarticle. The hydrophilic coating can be coated on a substrate which maybe selected from a range of geometries and materials. The substrate mayhave a texture, such as porous, non-porous, smooth, rough, even oruneven. The substrate supports the hydrophilic coating on its surface.The hydrophilic coating can be on all areas of the substrate or onselected areas. The hydrophilic coating can be applied to a variety ofphysical forms, including films, sheets, rods, tubes, molded parts(regular or irregular shape), fibers, fabrics, and particulates.Suitable surfaces for use in the invention are surfaces that provide thedesired properties such as porosity, hydrophobicity, hydrophilicity,colorisability, strength, flexibility, permeability, elongation abrasionresistance and tear resistance. Examples of suitable surfaces are forinstance surfaces that consist of or comprise metals, plastics,ceramics, glass and/or composites. The hydrophilic coating may beapplied directly to the said surfaces or may be applied to a pretreatedor coated surface where the pretreatment or coating is designed to aidadhesion of the hydrophilic coating to the substrate.

In one embodiment of the invention the hydrophilic coating according tothe invention is coated on a biomedical substrate. A biomedicalsubstrate refers, in part, to the fields of medicine, and the study ofliving cells and systems. These fields include diagnostic, therapeutic,and experimental human medicine, veterinary medicine, and agriculture.Examples of medical fields include ophthalmology, orthopedics, andprosthetics, immunology, dermatology, pharmacology, and surgery;non-limiting examples of research fields include cell biology,microbiology, and chemistry. The term “biomedical” also relates tochemicals and compositions of chemicals, regardless of their source,that (i) mediate a biological response in vivo, (ii) are active in an invitro assay or other model, e.g., an immunological or pharmacologicalassay, or (iii) can be found within a cell or organism. The term“biomedical” also refers to the separation sciences, such as thoseinvolving processes of chromatography, osmosis, reverse osmosis, andfiltration. Examples of biomedical articles include research tools,industrial, and consumer applications. Biomedical articles includeseparation articles, implantable articles, and ophthalmic articles.Ophthalmic articles include soft and hard contact lenses, intraocularlenses, and forceps, retractors, or other surgical tools that contactthe eye or surrounding tissue. A preferred biomedical article is a softcontact lens made of a silicon-containing hydrogel polymer that ishighly permeable to oxygen. Separation articles include filters, osmosisand reverse osmosis membranes, and dialysis membranes, as well asbio-surfaces such as artificial skins or other membranes. Implantablearticles include catheters, and segments of artificial bone, joints, orcartilage. An article may be in more than one category, for example, anartificial skin is a porous, biomedical article. Examples of cellculture articles are glass beakers, plastic petri dishes, and otherimplements used in tissue cell culture or cell culture processes. Apreferred example of a cell culture article is a bioreactormicro-carrier, a silicone polymer matrix used in immobilized cellbioreactors, where the geometry, porosity, and density of theparticulate micro-carrier may be controlled to optimize performance.Ideally, the micro-carrier is resistant to chemical or biologicaldegradation, to high impact stress, to mechanical stress (stirring), andto repeated steam or chemical sterilization. In addition to siliconepolymers, other materials may also be suitable. This invention may alsobe applied in the food industry, the paper printing industry, hospitalsupplies, diapers and other liners, and other areas where hydrophilic,wettable, or wicking articles are desired.

The medical device can be an implantable device or an extracorporealdevice. The devices can be of short-term temporary use or of long-termpermanent implantation. In certain embodiments, suitable devices arethose that are typically used to provide for medical therapy and/ordiagnostics in heart rhythm disorders, heart failure, valve disease,vascular disease, diabetes, neurological diseases and disorders,orthopedics, neurosurgery, oncology, ophthalmology, and ENT surgery.

Suitable examples of medical devices include, but are not limited to, astent, stent graft, anastomotic connector, synthetic patch, lead,electrode, needle, guide wire, catheter, sensor, surgical instrument,angioplasty balloon, wound drain, shunt, tubing, infusion sleeve,urethral insert, pellet, implant, blood oxygenator, pump, vasculargraft, vascular access port, heart valve, annuloplasty ring, suture,surgical clip, surgical staple, pacemaker, implantable defibrillator,neurostimulator, orthopedic device, cerebrospinal fluid shunt,implantable drug pump, spinal cage, artificial disc, replacement devicefor nucleus pulposus, ear tube, intraocular lens and any tubing used inminimally invasive surgery.

Articles that are particularly suited to be used in the presentinvention include medical devices or components such as catheters, forexample intermittent catheters, balloon catheters, PTCP catheters, stentdelivery catheters, guide wires, stents, syringes, metal and plasticimplants, contact lenses and medical tubing.

The invention will be further illustrated by the following examples,without being limited thereto.

EXAMPLES I-V AND COMPARATIVE EXPERIMENTS A-C Primer Coating Formulation

The primer formulation was prepared by dissolving the components belowin ethanol.

PTGL1000 (T-H)₂ oligomer 4.25% (w/w) PVP K85 (supplied by BASF) 0.75%(w/w) Irgacure 2959 (supplied by Sigma Aldrich) 0.20% (w/w) Ethanol 96%(supplied by Merck) 94.8% (w/w)

The synthesis of PTGL1000(T-H)₂ oligomer is described in WO2007/065722.

Hydrophilic Coating Formulation

The hydrophilic coating formulation was prepared by dissolving thecomponents below in a water/ethanol mixture 1:1 based on weight.

Weight % PVP K85 5.2 Polyacrylamide-co-acrylic acid sodium salt (PAcA)0.35 (supplied by Sigma Aldrich) Irgacure 2959 (supplied by SigmaAldrich) variable (see table 1 below) Norrish Type II photoinitiatorvariable (see table 1 below) Ethanol (96%) 49 Water 45

TABLE 1 Composition hydrophilic top coatings in weight % based on dryweight of the coating Example/Experiment A B C I II III IV V Irgacure2959 3 0 1 0 0 0 1 1 Benzophenone 0 2 1 0 0 0 0 0 3-benzoyl benzoic acid0 0 0 2 0 0 1 0 4-benzoyl benzoic acid 0 0 0 0 2 0 0 03,3′,4,4′-benzophenone 0 0 0 0 0 2 0 1 Tetracarboxylic acid anhydride

Coating Application

PVC tubes, supplied by Raumedic, with a diameter of 14 Fr and a lengthof 40 cm were coated on a Harland PCX coater 175/24.

The PVC tubes were first dip-coated with the primer coating formulationand cured according the dip protocol for the primer in table 2.Subsequently the hydrophilic coating formulation was applied and curedaccording the dip protocol for the hydrophilic coating. Temperature andhumidity during application were respectively 21° C.+/−2° C. and40%+/−15%.

The Harland PCX coater/175/24 was equipped with a Harland Medicalsystems UVM 400 lamp. Intensity of the lamps of the Harland PCXcoater/175/24 was on average 60 mW/cm² and was measured using a SolatellSola Sensor 1 equipped with an International Light detector SED005#989,Input Optic: W#11521, filter: wbs320#27794. The IL1400A instructionmanual of International Light was applied, which is available on theinternet: www.intl-light.com. For the applied parameters in the PCXcoater see Table 2.

TABLE 2 Applied parameters in the PCX Coater Coating parametersselection table Hydrophilic Dipping Cycle Primer coating coating Movedevice carrier to position (cm) 125 125 Speed (cm/sec) 6.5 6.5accelaration (sec) 0.1 0.1 Move device carrier down (cm) 11.5 11.5 speed(cm/sec) 4 2 accelaration (sec) 0.1 0.1 Move device carrier down (cm)27.5 27.5 speed (cm/sec) 2 2 accelaration (sec) 0.1 0.1 Time Pause (sec)10 10 Move device carrier up (cm) 28.5 28.5 speed (cm/sec) 0.3 1.5accelaration (sec) 0.1 0.1 Move device carrier to position (cm) 148 148speed (cm/sec) 6.5 6.5 accelaration (sec) 0.1 0.1 Cure Cycle Rotator On(rpm) 2 2 UV lights Full Power Drying time (sec) 90 90 Time pause (sec)30 Varied: 180, 240 or 360 Close Shutter UV lights Standby Power RotatorOff

Test Methods Lubricity Test

Lubricity tests were performed on a Harland FTS5000 Friction Tester(HFT). The protocol was selected: see Table 3 for HFT settings. Frictiontester pads were used from Harland Medical Systems, P/N 102692, FTS5000Friction Tester Pads, 0,125*0,5**0,125, 60 durometer.

Subsequently the desired test description was inserted when “run test”was activated. After inserting the guidewire into the catheter, thecatheter was attached in the holder. The device was jogged down to thedesired position and the catheter was soaked in demineralized water for1 min. After zero gauging in water the protocol was activated by pushing“start”. The data were saved after finishing. The holder was removedfrom the force gauge and subsequently the catheter was removed from theholder.

TABLE 3 HFT settings Transport movement (cm) 10 Clamp force (g) 300 Pullspeed (cm/s) 1 Acceleration time (s) 2 Number of rubs 25

The measured coefficient of friction (COF) after 25 rubs is used to rateperformance of the coating. The COF is defined as the measuredfriction/clamp force.

A COF<0.05 is judged as good. A COF between 0.05 and 0.1 is judged astoo high; a COF>0.1 is judged as bad.

Feel Test

The coating was also evaluated after being wetted by rubbing gently withthe fingers. A coating that is insufficiently cured releases a lot ofsticky material and defects are easily induced.

Rating in the Feel Test

-   Good: no leachables, no defects induced after rubbing or HFT test-   Reasonable some leachables indicated as slight sticky feeling, few    defects that are difficult to be felt-   Bad: clear sticky feeling, defects clearly felt as area's where    coating is rubbed away or damaged-   Very bad: fingers are covered with a sticky mass, many severe    defects (most severe case is that the coating integrity is so bad    that the coating dissolves in water)

Experimental Results

TABLE 4 Performance of coatings produced with a cure time of 240 s forthe top coat. Formulation COF Feel test A >0.1 Very bad B >0.1 Very badC >0.1 Very bad I 0.03 Good II 0.03 Good III 0.03 Good IV 0.03 Good V0.03 Good

TABLE 5 Performance of coatings produced with a cure time of 180 s forthe top coat. Formulation COF Feel test A >0.1 Very bad B >0.1 Very badC >0.1 Very bad I >0.1 Very bad II >0.1 Very bad IV 0.03 Reasonable V0.03 Good

1. Coating formulation for preparing a hydrophilic coating comprising ahydrophilic polymer, a Norrish Type II photoinitiator, comprising asubstituted benzohenone, xanthone, tioxanthone or anthraquinone, andmore than 70 wt % of a carrier liquid.
 2. Coating formulation accordingto claim 1, wherein the Norrish Type II photoinitiator comprises one ormore substituents on the 3 and/or 4 position of the phenyl rings. 3.Coating formulation according to claim 1, wherein the Norrish Type IIphotoinitiator is chosen from the group 2-benzoyl benzoic acid,3-benzoyl benzoic acid, 4-benzoyl benzoic acid, 3,3′,4,4′-benzophenonetetracarboxilic acid, 4-benzoyl-N,N,N,-trimethylbenzene-methaminiumchloride, 2-hydroxy-3-(4-benzoylphenoxy)-N,N,N-trimethyl-1-propanaminiumchloride,2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthon-2-yloxy)-N,N,N-trimethyl-1-propanaminiumchloride, thioxanthone-3-carboxylic acid, thioxanthone-4-carboxylicacid, anthraquinone 2-sulfonic acid, 9,10-anthraquinone-2,6-disulphonicacid, anthraquinone-2-sulfonic acid, anthraquinone-2-carboxylic acid andsalts of these photoinitiators such as the sodium-, potassium-,calcium-, magnesium, iron-, copper and zinc salts.
 4. Coatingformulation according to claim 1, wherein the coating formulation alsocomprises a Norrish Type I photoinitiator.
 5. Coating formulationaccording to claim 4, wherein the Norrish Type I photoinitiator ischosen from the group consisting of benzoin derivatives, methylolbenzoin and 4-benzoyl-1,3-dioxolane derivatives, benzilketals,α,α-dialkoxyacetophenones, α-hydroxy alkylphenones,α-aminoalkylphenones, acylphosphine oxides, bisacylphosphine oxides,acylphosphine sulphides, and halogenated acetophenone derivatives. 6.Coating formulation according to claim 1, wherein the hydrophilicpolymer is selected from the group consisting of poly(lactams), forexample polyvinylpyrollidone (PVP), polyurethanes, homo- and copolymersof acrylic and methacrylic acid, polyvinyl alcohol, polyvinylethers,maleic anhydride based copolymers, polyesters, vinylamines,polyethyleneimines, polyethyleneoxides, poly(carboxylic acids),polyamides, polyanhydrides, polyphosphazenes, cellulosics, for examplemethyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, andhydroxypropylcellulose, heparin, dextran, polypeptides, for examplecollagens, fibrins, and elastin, polysacharrides, for example chitosan,hyaluronic acid, alginates, gelatin, and chitin, polyesters, for examplepolylactides, polyglycolides, and polycaprolactones, polypeptides, forexample collagen, albumin, oligo peptides, polypeptides, short chainpeptides, proteins, and oligonucleotides and blends or copolymershereof.
 7. Coating formulation according to claim 1, wherein the coatingformulation further comprises a polyelectrolyte.
 8. Method of forming ahydrophilic coating on a substrate, the method comprising applying acoating formulation according to claim 1 to at least one surface of anarticle and allowing the coating formulation to cure for a time periodless than 360 seconds.
 9. Method according to claim 8, wherein curing isperformed by exposing the formulation to electromagnetic radiation,preferably to UV radiation.
 10. Hydrophilic coating obtainable by curinga hydrophilic coating formulation according to claim
 1. 11. Lubriciouscoating obtainable by applying a wetting fluid to a hydrophilic coatingaccording to claim
 10. 12. Article comprising at least one hydrophiliccoating or lubricious coating according to claim
 10. 13. Articleaccording to claim 12, wherein the article is a medical device orcomponent.
 14. Medical device or component according to claim 13comprising a catheter, a medical tubing, a guide wire, a stent, or amembrane.